The disclosure relates to a flow regulating valve subassembly.
A control valve subassembly of this type is known from U.S. Pat. No. 4,779,836. It comprises a housing 1, in which a valve piston 13 is accommodated linearly movably. Provided on the housing are a first and a second working connection 2; 3 which are connected to one another via a valve seat on the housing. The valve seat can be closed by the valve piston by means of a first end face 14, while the opposite second end face 16, acting in the closing direction, of the valve piston 13 delimits, together with the housing, a valve space 17. Between the housing and the valve piston, an adjustable throttle 18 is provided, the throttle cross section of which changes continuously during displacement of the valve piston 13. For this purpose, notches 18 which run in the direction of the valve piston axis and the depth of which changes continuously are provided on the circular-cylindrical outer circumferential surface of the valve piston 13. The notches 18 are designed such that, when the valve piston 13 sealingly closes the valve seat, a residual throttle cross section remains, so that there is always a fluid connection between the first working connection 2 and the valve space 17.
In the stationary state of the valve subassembly, the position of the valve piston 13 is set such that the force which the pressure in the valve space 17 exerts upon the second end face 16 is equal to the force which the pressures of the first and of the second working connection 2, 3 exert in the opening direction upon the valve piston 13. The pressure of the first working connection 2 acts in this case upon a central circular surface 14, while the pressure of the second working connection 3 acts upon a surrounding annular surface 15. The circular surface 14 and the annular surface 15 are delimited with respect to one another by the valve seat.
The pressure in the valve space 17 arises from the pressure of the first working connection 2, reduced by the amount of the pressure drop in the throttle 18 to which the fluid is delivered via the duct 19 arranged in the valve piston 13. The pressure drop of the throttle 18 arises from the volume flow which flows via the throttle 18. This volume flow is equal to the control volume flow which flows out of the valve space 17 via a pilot control valve 26 to the second working connection 2. The variable 5 throttle cross section, which increases essentially in proportion to the opening of the valve piston 13, has the effect that the said control volume flow is proportional to the main volume flow which flows from the first working connection 2 to the second working connection 3. Since the control volume flow is markedly lower than the main volume flow, the present valve subassembly is a volume flow intensifier. For the sake of completeness, reference may also be made of the nonreturn valves 21; 22; 27; 28 which enable the valve subassembly also to be operated with an opposite main flow direction, that is to say from the second working connection 3 to the first working connection 2.
The pilot control valve 26 is often activated electrically, a desirable operating behavior of the flow regulating valve subassembly being one in which the main volume flow depends solely on the activation signal of the pilot control valve 26, so that a volume flow actuator is obtained. However, this is only approximately the case, since the control volume flow depends not only on the position of the pilot control valve 26, but also on the pressure drop at the pilot control valve 26, this pressure drop depending, in turn, on the pressure of the first working connection 2.
This dependence can be compensated via pressure sensors which have to be of highly accurate design and are consequently costly.
Furthermore, this effect can be eliminated partially by load compensation of the pilot control valve by means of a pressure balance. The flow regulating valve subassembly nevertheless is still dependent upon the pressures in the working connections.
The object of the present disclosure is to provide a flow regulating valve subassembly in which accurate determination of the main volume flow is always made possible.